I have a question, I've done walls, Floors etc.. But I never layed concrete down, I brought a house in Texas that came with a 10 by 10 patio slab in the yard, I would like to extend it to 20by20, the question is will I need other materials other then quikrete? Will I need to add something due to the heat? Will I need to lay gravel? Any advice you can give would be greatly appreciated.